Computer Assisted Surgery (CAS) systems are being increasingly used for orthopedic operations in general, and for joint replacement surgeries in particular, in order to continue to improve the accuracy and long-term success of joint replacement surgery. The accuracy of cuts and drilled holes performed in joint replacement surgeries such as in knee arthroplasty, or total knee replacement, is of prime importance, such that the installation of the implants can be made such that they best duplicate the kinematics of the natural knee.
Known optical, radio frequency and magnetic based CAS systems employ passive and active trackable elements affixed to objects, such as surgical tools and patient bone references, in order to permit the determination of position and orientation of the objects in three-dimensional space. Preoperatively taken images, computer generated models created from preoperative patient scans or intra operative landmark digitization are some of the methods used to provide accurate patient anatomical information to the CAS system, such that the real-time position of the same anatomical elements can be registered or calibrated and thus tracked by the system, permitting the display to the surgeon of these elements relative to the surgical tools used during the surgery.
Total knee replacement surgery, for example, may require one or more precise cuts to be made in the femur and/or tibia to completely remove the knee joint, such that the implant may fit correctly and best replicates the geometry of a natural healthy knee. To perform these steps, in both conventional and CAS total knee replacement surgeries, it is known to use a tool or implement known as a surgical tool guide block which provides a drill and/or cutting guide to assist the surgeon to perform the steps required to prepare the femur and tibia for receiving the implant. For example, using known CAS surgery techniques, the surgical tool guide block, such as a saw cutting guide for example, would be drilled or screwed into that part of the bone to be severed, while in other bone CAS systems, and its position would be determined through known methods using the CAS system.
To best permit the desired positioning and fixation of the surgical tool guide block in the determined position, a surgeon typically uses a positioning block which requires controllable adjustment of several degrees of freedom.
While certain flexibility is provided by such total knee replacement positioning blocks of the prior art, there nevertheless remains a need for an improved positioning device permitting additional control of the adjustment thereof, and being adapted for use with a CAS system.